Living with Deep Foundation Defects

Abstract

Defect details in bored pile and drilled pier foundations are presented for multiple installation methods to a depth of 70 ft (22 m) in projects along the Texas Gulf Coast. Over 2000 bored pile and drilled pier foundations covering four projects are reviewed. For nearly five decades drilled pier soldier pile walls have been an economic alternate to the reinforced concrete slurry wall which has enjoyed wide spread popularity across the North American Continent; hence the bored pile and drilled pier foundations used to form a basement wall on a project are numerous and are each exposed to the bottom basement level as construction proceeds. The experiences of design, preparation of construction documents and construction geotechnical engineering along with exposure allow a unique assessment of the design and construction compatibility of the completed drilled piers and bored piles. One project includes the observed limitations of low strain nondestructive testing to assess the presence of soldier pile defects for 24 in. (50 cm) diameter bored piles. Bored pile and drilled pier foundation defects are complex and do not lend themselves to easy assessment by non destructive testing. Accordingly, it is concluded that defects in bored pile and drilled pier foundation construction are inherent and that control of the construction means and methods is the only rational means available to build deep foundations with manageable defects. Hidden defect factors or reduced structural factors are needed for the design of deep foundations which will limit concrete carrying capacity below column design values because of the construction limitations, but the hidden defect factor cannot be a replacement for the control of construction means and methods by rational construction geotechnical engineering.